The invention relates to a transmission with a transmission input shaft and a transmission output shaft and two power transmission paths between the transmission input shaft and a main gear set consisting of two single planetary gear sets with four shafts identified in order of speed as first, second, third and fourth shaft, wherein the first of the power transmission paths exhibits a first fixed transmission ratio and the second of the power transmission paths exhibits a second fixed transmission ratio, wherein the second fixed transmission ratio is lower than the first fixed transmission ratio.
In addition the invention relates to a hybrid drive train for a motor vehicle comprising at least one internal combustion engine and at least one electric machine.
A transmission of the initially named type is known, for example, from EP 0 434 525 A1. In the known transmission which exhibits five shifting elements, whose selective pair by pair engagement causes different transmission ratios between the transmission input shaft and the transmission output shaft, six forward gears and one reverse gear are implemented.
Furthermore, a hybrid drive train with an internal combustion engine and a plurality of electric motors is known from patent application DE 10 2010 028 026 of the applicant for this patent. In this hybrid drive train a gear transmission with partial transmissions is used, each of said partial transmissions exhibiting a shiftable gear stage. The shiftable gear stages present in the partial transmissions are provided by a direct gear with coaxial input and output, each of which being generated by precisely one single transmission, such as a spur gear pair or a planetary transmission. A nine-gear countershaft transmission with coaxial output would accordingly require at least nine single transmissions for the nine gears in the form of nine spur gear pairs.
Therefore, one of the problems addressed by the invention is the problem of reducing the required design and construction costs for a hybrid drive train of the type mentioned above with a multiple speed transmission.
This problem is solved according to the invention with a transmission of the initially named type by connecting at least one electric machine to one of the shafts of the main gear set, wherein the first shaft can be connected via a first shifting element to a first power transmission path and via a second shifting element to a second power transmission path, wherein the second shaft can be connected via a third shifting element to the first power transmission path and via a fourth shifting element to the second power transmission path, wherein the third shaft is continuously connected to the transmission output shaft, wherein the fourth shaft can be fixed via a sixth shifting element and can be connected via a fifth shifting element to the first power transmission path or the second power transmission path.